PROJECT SUMMARY/ABSTRACT For a long time, the study of Alzheimer?s disease (AD) in humans has been hampered by the fact that absolute AD diagnosis could only be ascertained by assessment of brain pathology upon autopsy. More recently, imaging agents have become available that allow direct imaging of the two hallmarks of AD (amyloid plaques and tau tangles) in living humans. However, these imaging agents are expensive and invasive for use in routine diagnostics. The need for low-cost blood based diagnostic assays has never been greater. C2N Diagnostics has been developing mass spectrometry based assays that investigate amyloid beta peptides in biofluids since 2007. Recent advances in sample cleanup, purification of amyloid beta, and mass spectrometry instrumentation have made it possible to reliably quantify amyloid beta in human plasma samples. Preliminary data from Dr. Randall Bateman?s laboratory at Washington University shows that the ratio of two amyloid beta peptides in plasma can predict the presence of amyloid plaques in the brain. This technology could revolutionize the field of AD diagnostics, and when presented at the Alzheimer?s Association International Conference in July 2017, this discovery was pronounced as ?by far the biggest news of the meeting? by one of the key opinion leaders in AD clinical research. The specific aims of this SBIR Fast-Track application are to analytically and clinically validate C2N?s plasma assay for use as a diagnostic test for predicting brain amyloidosis.